The Hep A/B vaccinations are actually quite handy for general life - not just travelling. I've been through the various injections with no side-effects.
Note the combined shot is around $80 x 3 plus perhaps a doctor's visit fee or three, so it's not cheap. At least Medibank gave me some rebate on it via my package plus options.
I would also recommend Chickenpox and Measles vac's if you havn't been through those in childhood. Having caught Chickenpox a few years ago in Singapore (I suspect), and experiencing it in adulthood was not a fun experience. At least I managed to get back to Australia for a couple of days before the rash/effects started - otherwise I would have been quarantined in my hotel room for around a week!
MD TravelHealth website also recommends similar vax's to what
JohnK suggests.
MD Travel Health - Thailand - vaccinations, malaria, safety, and other medical advice
Malaria shouldn't be a concern if not going into very rural forestry type areas.
You can also get vaccinations over in Bangkok for pretty good prices compared to Australia - for example at the Red Cross centre attached to the Snake Farm. But of course immunity isn't instant, so you need several weeks or multiple shots in some cases to get resistance. I have no experience of getting shots there, but looked into it a couple of years ago, and will probably get the Yellow Fever and a couple of catch up shots next time I'm in BKK.
Note none of this advice should substitute for you visiting a travel doctor or your local doctor for advice over which vaccinations you should get...